Many industrial processing lines utilize an input material which is fed thereto from a coil. As the coil is depleted, its outer diameter changes and therefore the instantaneous diameter of the coil of material may be used to control functions of the processing line. Typical of such operations are those which utilize a strip material, such as a metallic strip material, as an input and require that the strip be continually fed thereto. This strip is available from a coil which is payed out until depleted. Because it would be highly undesirable to stop the processing line upon each depletion of a coil, variously configured strip accumulators have been developed which receive strip from the input coil and hold or store a certain amount thereof while at the same time paying out strip so held to the processing line. Such accumulators are thus intended to permit the processing line to remain active during the time a new input strip coil is attached, as by welding, to the end of the coil which has just been depleted. A typical accumulator which is very popular is shown in the U.S. Pat. No. 3,506,210.
So that there is maximum amount of time for the new coil to be attached to the old coil, it is important that the accumulator be controlled so that it is filled substantially to its capacity at the time a coil is depleted. At first no such control was available with only a sensing device being provided to detect the end of a coil of strip before it reached the accumulator so that the feed to the accumulator could be stopped for the welding process. Such a sensing device is disclosed in said U.S. Pat. No. 3,506,210 but did not, of course, provide any guarantee that the accumulator would be full at the time of welding.
A significant advancement in accumulator control is found in U.S. Pat. No. 3,888,430. There a pivoting arm rested on the coil and contacted a series of limit switches as the coil became depleted to control the accumulator. While this mechanical device has met with commercial success, from a practical standpoint it is not without its problems. First, some materials are not suited for the physical contact of an arm because they are easily scratched. Such scratching of any material was often prevalent when a coil was out-of-round, as is often the case. In this situation the arm would tend to bounce not only damaging the material but inducing false tripping of the limit switches. At high speeds with out-of-round coils, the arm would tend to stay out of contact with the coil inducing further false limit switch actuation. Additional false alarms and/or damage to the arm often occurred due to potential interference between the arm and the strip edge guides on the uncoiler. Such could be particularly prevalent with strip of narrow width where the edge guides would be closer to the arm.
In addition, this mechanical device was not conveniently and accurately settable. Every time a different gauge strip was utilized the limit switches had to be repositioned. Such was not only a time-consuming procedure but it also lacked in precision in that a misplacement of a few thousandths of an inch could result in a significant difference in strip material, particularly, that of thin gauge. Of course, the mechanical placement of a limit switch to thousandths of an inch accuracy is highly unlikely.
Finally, the use of the mechanical pivoting arm often took away valuable physical space in the processing line with some lines not having the room for the placement of the arm. In those areas where there was room for such devices, the arms could be damaged by a careless malpositioning of the arm on the coil or other activities in the area. Thus, while the device of U.S. Pat. No. 3,888,430 represented an important step in accumulator control, its effectiveness, accuracy and efficient use was somewhat limited.